The use of wireless communication devices such as telephones, pagers, personal digital assistants, laptop computers, etc., hereinafter referred to collectively as “mobile appliances” or “mobile stations” interchangeably, has become prevalent in today's society. Recently, at the urging of public safety groups, there has been increased interest in technology which can determine the geographic position, or “geolocate” a mobile appliance in certain circumstances. For example, the Federal Communication Commission (“FCC”) has issued a geolocation mandate for providers of wireless telephone communication services that puts in place a schedule and an accuracy standard under which the providers of wireless communications must implement geolocation technology for wireless telephones when used to make a 911 emergency telephone call (FCC 94-102 E911).
In addition to E911 emergency related issues, wireless telecommunications providers are developing location-enabled services for their subscribers including roadside assistance, turn-by-turn driving directions, concierge services, location-specific billing rates and location-specific advertising.
To support FCC E911 rules to locate wireless 911 callers, as well as the location enabled services, the providers of wireless communication services are installing mobile appliance location capabilities into their networks. FIG. 1a shows a wireless communication network 100 with a typical network overlay location architecture.
Wireless communication systems typical include a mobile station (MS) 110, a plurality of base stations (BS) 120a–c, a base station controller (BSC) 130, and a mobile switching center (MSC) 140. The wireless communication system allows communication between the mobile station and the base station over an air interface as is well known in the art. The network overlay location system is made up of a plurality of local measurement units (LMU) 150, also known as wireless location sensors (WLS), a geo-location system controller (GCS), also known as a Serving Mobile Location Center (SMLC), 160 and a mobile positioning center (MPC), also known as a Gateway Mobile Location Center (GMLC), 170 and, depending on the air interface, an Abis measuring unit (AMU) 180. In this architecture, a wireless handset location is produced for a single carrier. FIG. 1b shows a representation of the system with a representative base station 120.
The LMUs 150a–c of the geo-location network overlay are generally located at the wireless service provider's base stations. The LMUs 150a–c take measurements on the radio signal emitted by the mobile station (MS) 110 under control of the GCS. The GCS is commanded to take locations and report locations by the MPC 170 for specific handsets. The AMU 180 provides information on the radio channel assignments for the mobile station for certain air interfaces (GSM, iDEN, for example, and others). For other air interfaces (IS-136, IS-95, AMPS, lxrtt, for example, and others) the radio channel assignment information is provided by the MPC.
Mobile appliances do not all operate using a common wireless air interface protocol standard. The Telecommunications Industry of America (“TIA”) and the European Telecommunications Standard Institute (“ETSI”) are well known standards organizations, each publishing recognized wireless air interface protocol standards. As is known in the art, TIA and ETSI are two examples of standards bodies. Others include the Third Generation Partnership Project (“3GPP”) and Third Generation Partnership Project 2 (“3GPP2”). In the past, mobile appliance geolocation implementations have been specific to the underlying wireless air interface protocol standard (i.e., network reference models, interfaces, messages, etc.) utilized by the mobile appliance being located.
In operation, typical network overlay location systems take measurements on radio frequency transmissions from the mobile station at base station locations surrounding the mobile appliance, and estimate the location of the mobile appliance with respect to the base stations. Because the geographic location of the base stations is known, the determination of the location of the mobile appliance with respect to the base station permits the geographic location of the mobile appliance to be determined. The radio frequency measurements of the transmitted signal at the base stations can include, for example, the time of arrival, time difference of arrival, the angle of arrival, the signal power, or the unique/repeatable radio propagation path (radio fingerprinting) derivable features. In addition, the geolocation systems can also use collateral information, e.g., information other than that derived from the radio frequency measurement to assist in the geolocation of the mobile appliance, i.e., location of roads, dead-reckoning, topography, map matching etc.
In a network-based geolocation system, the mobile appliance to be located is typically identified and radio channel assignments determined by (a) monitoring the control information transmitted on radio channel or wireline interface for telephone calls being placed by the mobile appliance to detect calls of interest, i.e., 911, (b) a location request provided by a non-mobile appliance source, e.g., an enhanced services provider. Once a mobile station to be located has been identified and radio channel assignments determined, the GCS may typically be tasked to determine the geolocation of the mobile appliance and then directed to report the determined position to the MPC (or the requesting entity or enhanced services provider).
The monitoring of the radio frequency transmissions from the mobile appliance to identify calls of interest is known as “tipping”, and generally involves recognizing a call of interest being made from a mobile appliance and collecting the call setup information. Once the mobile appliance is identified and the call setup/channel assignment information is collected, the location determining system can be tasked to geolocate the mobile appliance.
It is often the case that several wireless communication systems or carriers occupy the same market or geographic region. However, the geo-location architecture shown in FIG. 1, would be unable to locate a mobile station which was not being provided service by the host wireless network because the MPC 140 would not be configured to task the GCS 160 to locate the call, and the AMU 180 would not have access to the radio channel assignments. Furthermore, the LMUs 150a–c may not have access to the radio frequency band for the operating MS. Thus, wireless carriers in a given market desiring to provide services related to mobile subscriber location where the mobile subscriber is either within the wireless carrier's system or on a different wireless system, would have to equip their network with location assets thereby unnecessarily duplicating assets and capability, all at a substantial cost. Therefore, there is a need for a geolocation system operable on multiple carriers.
In order to meet this need and obviate the deficiencies of the prior art, it is an object of the disclosed subject matter to provide a common network overlay system that can serve multiple carriers at a reduced cost and complexity over the normal practice of having a dedicated geo-location system.
It is also an object of the disclosed subject matter to present a novel network overlay geolocation system capable of geolocating a first and a second mobile station operating in a geographic area serviced by a first and a second wireless communication system, respectively. The system may include a plurality of LMUs, at least one MPC, and a geolocation controller, where the first mobile station communicates over the first wireless communication system and the second mobile station communicates over the second wireless communication system. The MPC of the system may be configured to task the geolocation controller to locate the first and/or second mobile station.
It is a further object of the disclosed subject matter to present a novel method for geolocating a target mobile station in a geographic area serviced by a plurality of wireless communication systems. The method may include transmitting a signal from the target mobile station to one of the wireless communication systems, tasking the geolocation controller to locate the target mobile, and configuring the LMUs to measure an attribute of the signal of the target mobile station based on call set up information for the call from the target mobile station and an attribute of the serving wireless communication system. The novel method locates the target mobile based at least in part on the measured attribute.
It is still another object of the disclosed subject matter to present a novel method for selecting a set of LMU locations from a plurality of possible LMU locations in a geographic area serviced by a plurality of wireless communication systems. The novel method includes the steps of modeling a coverage plan for each of the plural wireless communication systems over the geographic area, selecting plural LMU locations from the plurality of possible LMU locations to thereby provide a candidate set of LMU locations, and simulating the operational performance of each of the candidate sets of LMU locations over the geographic area for each of the plural wireless communication systems. The novel method may also compare the simulated operational performances of the candidate sets of LMU locations to thereby determine and select an optimal set of LMU locations, i.e., the set of LMU locations with an optimal simulated operational performance.
It is another object of the disclosed subject matter to present, in a network overlay geolocation system for determining the geolocation of mobile stations associated with a first wireless communication system having a first plurality of base stations where the geolocation system includes LMUs located at ones of the first plurality of base stations, a novel method for determining the geolocation of a mobile station associated with a second wireless communication system. The novel method includes (a) modeling a coverage plan for the second wireless communication system using said LMUs to thereby obtain a simulated geolocation performance parameter, (b) evaluating the simulated parameter and if the evaluation is unacceptable, modeling the coverage plan for the second wireless communication system using said LMUs and at least one additional LMU located at a base station associated with the second wireless communication system to thereby obtain a simulated geolocation performance parameter, (c) repeating step (b) until the evaluation is acceptable, and (d) locating said at least one additional LMU at the base station associated with the second wireless communication system according to the remodeled coverage plan so as to determine the geolocation of a mobile station associated with the second wireless communication system.
It is yet another object of the disclosed subject matter to present, in a network overlay geolocation system for determining the geolocation, within a predetermined accuracy, of mobile stations associated with a first wireless communication system, a novel method for determining the need for additional LMU(s) to determine the geolocation, within the predetermined accuracy, of a mobile station associated with a second wireless communication system. The novel method may include modeling a coverage plan for the second wireless communication system using the LMUs of the first wireless communication system to thereby simulate the accuracy of a geolocation determination of a mobile station associated with the second wireless communication system. The method may also include evaluating the simulated accuracy against the predetermined accuracy and if the evaluation is unacceptable, modeling the coverage plan for the second wireless communication system using the LMUs of the first wireless communication system and at least one additional LMU located at a base station associated with the second wireless communication system to thereby simulate the accuracy of the geolocation determination of the mobile station associated with the second wireless communication system. The method additionally may include repeating the previous step until the evaluation is acceptable to thereby determine the need for an additional LMU.
It is still another object of the disclosure to present an improved network overlay geolocation system for locating a first mobile station associated with a first wireless communication system covering a geographic area. The improved system may include configuring the geolocation system to locate a second mobile station associated with a second wireless communication system covering at least a portion of the geographic area.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the disclosure pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.